Abstract: The carbonate rock distribution area in Guangxi is a typical area with high geological background of heavy metals in soils. The nonferrous metal smelting activities in this area further enhance heavy metal accumulation in soils. Clarifying the contribution of smelting activities and geological background to regional soil heavy metal pollution is critically needed. In this study, we examined the distribution characteristics and potential ecological risks of heavy metals (Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni) in soils in a nonferrous metal smelting area with typical geological background. The source and contribution rate of heavy metals were analyzed by the traceability method. The results showed that the main pollutants were Cd, Zn, As and Pb, and that the areas with heavy excess of Cd in surface soil were at a state of intensive ecological risk. The smelting activities were the main sources of Cd, Hg, As, Pb, Cu and Zn in soil. The presence of Cr and Ni was mainly contributed to the high geological background. The contribution rates of geological background factors to Cd, Hg, As, Pb, Cr, Cu, Zn and Ni were 4.8%, 71.7%, 33.6%, 31.0%, 92.4%, 76.5%, 27.3% and 99.3%, respectively. The contribution rates of human factors were 95.2%, 28.3%, 66.4%, 69.0%, 7.6%, 23.5%, 72.7% and 0.7%, respectively. Our results provide support for accurately evaluating the risk of heavy metal pollution and formulating scientific prevention and control measures of soil heavy metal pollution in carbonate mining areas.

Key words: nonferrous metal smelting, soil, heavy metal, ecological risk.